1. Field of the Invention
This invention relates to ink adapted to reduce the kogation, a scorched condition, of the surface of a heater for applying thermal energy to ink, to a method of preventing the kogation of the surface of a heater, to an ink-jet recording method, to an ink-jet recording apparatus, to a recording unit and also to a method of prolonging the service life of an ink-jet recording head.
2. Related Background Art
Various printing techniques using an ink-jet method have been proposed to date. Of the known ink-jet methods, the one described in Japanese Patent Application Laid-Open No. 54-51837 and adapted to discharge ink in the form of ink droplets under the effect of the thermal energy applied to the ink to be ejected from a recording head (so-called xe2x80x98bubble-jetxe2x80x99 method) is highly advantageous because it can produce high quality images on ordinary plain paper not having any specific coat layer at high speed and at low cost due to the fact that the high density multi-nozzle of the recording head has a very simple configuration. With the above identified method, the liquid on the heater of the recording head generates a bubble as the heater is heated rapidly and the volume of the bubble is rapidly increased to exert a power to the liquid so as to discharge ink droplets from the nozzle at the front end of the recording head. The discharged ink droplets are then made to adhere to a recording medium for printing.
However, the above identified method is accompanied by a drawback that, since the heater of the recording head is heated each time when ink is discharged from the recording head, a decomposition product of ink (so-called xe2x80x98kogaxe2x80x99) is deposited on the surface of the heater particularly when a large volume of ink is used with the recording head for printing. As koga is deposited, thermal energy is not effectively transmitted from the heater to the ink to be discharged from the recording head so that there can arise a problem that the rate at which ink droplets are discharged is reduced from the initial level in terms of both volume and velocity. Then, the recording head may have to be replaced particularly in the case of printing a large number of high quality images. Such a situation can end up with a rise of the printing cost to the user of the printing head.
Therefore, in the case of bubble jet recording method, it has been and still is a vital technical challenge to the industry to reduce the kogation of the surface of the heater of a recording head of the type under consideration that can give rise to the above identified problem and to prolong the service life of the recording head. For instance, Japanese Patent Application Laid-Open No. 3-160070 proposes ink containing oxo anions of an appropriate compound selected from phosphates, polyphosphates, esters of phosphoric acid (phosphates), arsenates, molybdates, sulfates, sulfites, oxalates and so on.
Under the above identified technological circumstances, it is therefore an object of the present invention to provide ink that can reduce the kogation of the surface of the heater of a recording head of the type under consideration that is produced when thermal energy is applied to the ink contained in the recording head in order to discharge the ink from the recording head.
Another object of the present invention is to provide a method of reducing the kogation of the surface of the heater of a recording head of the type under consideration that can be produced when thermal energy is applied to the ink contained in the recording head in order to discharge the ink from the recording head.
Still another object of the present invention is to provide an ink-jet recording apparatus that can print higher quality images than ever and prolong the service life of the recording head.
Still another object of the present invention is to provide a recording unit that can print high quality images with a prolonged service life.
A further object of the present invention is to provide a method for prolonging the service life of a recording head that can print high quality images at lower cost than ever.
According to the invention, the above objects are achieved by providing ink containing (a) a coloring material, (b) a liquid medium and (c) at least one compound selected from the group consisting of diglycollic acid and diglycollates.
In another aspect of the invention, there is provided a method of reducing the kogation of the surface of the heater of the recording head of an ink-jet printer, the heater being provided to apply thermal energy to the ink contained in the recording head in order to discharge the ink from an orifice, the heater having a top surface protecting layer containing a metal and/or a metal oxide, wherein the ink is ink for ink-jet printing and contains (a) a coloring material, (b) a liquid medium and (c) at least one compound selected from the group consisting of diglycollic acid and diglycollates.
According to the invention, it is now possible to effectively reduce the kogation of the top surface protecting layer of the heater. While it is not clear why ink according to the invention provides such an effect, the inventors of the present invention presume that the diglycollic acid in ink acts on the metal and/or the metal oxide of the top surface protecting layer of the heater and prevents koga from adhering to the surface or promotes decomposition of koga and exfoliation thereof from the surface of the heater.
As a result of an extensive study conducted by the inventors of the present invention, it has been found that the effect of the top surface protecting layer is very remarkable when tantalum and tantalum oxide are used respectively for the metal and the metal oxide. If the amount of energy applied to the heater is Eop and the minimal amount of energy that has to be applied to the heater in order to make the recording head discharge ink therefrom is Eth, it has been found that the koga prevention effect is maximized and the ink discharge durability of the recording head is remarkably improved when the amount of energy applied to the heater is so selected as to make the ratio of Eop/Eth satisfies the relationship defined below.
xe2x80x831.10xe2x89xa6Eop/Ethxe2x89xa61.80
In still another aspect of the invention, there is also provided an ink-jet recording method comprising a step of discharging ink from an orifice under the effect of thermal energy, wherein the ink to be used by the method is adapted to ink-jet recording and contains (a) a coloring material, (b) a liquid medium and (c) at least one compound selected from the group consisting of diglycollic acid and diglycollates.
In still another aspect of the invention, there is also provided an ink-jet recording apparatus comprising an ink-containing section for containing ink, an ink-jet recording head having a heater for applying thermal energy to the ink led from the ink-containing section and held in the ink path of the head and a means for applying a pulse-shaped electric signal to the heater according to the recording information given to it, the heater having a top surface protecting layer containing a metal and/or a metal oxide, wherein said ink is adapted to ink-jet recording and contains (a) a coloring material, (b) a liquid medium and (c) at least one compound selected from the group consisting of diglycollic acid and diglycollates.
In still another aspect of the invention, there is also provided a recording unit comprising an ink-containing section for containing ink and an ink-jet recording head adapted to discharge ink from an orifice under the effect of thermal energy, the ink-jet recording head being provided with a heater having a top surface protecting layer containing a metal and/or a metal oxide, wherein the ink is adapted to ink-jet recording and contains (a) a coloring material, (b) a liquid medium and (c) at least one compound selected from the group consisting of diglycollic acid and diglycollates.
In still another aspect of the invention, there is provided a method of prolonging the service life of a recording head to be used for an ink-jet recording method comprising a step of discharging ink from an orifice by applying thermal energy to ink, the recording head being provided with a heater for applying thermal energy to ink, the heater having a top surface protecting layer containing a metal and/or a metal oxide, wherein the ink is adapted to ink-jet recording and contains (a) a coloring material, (b) a liquid medium and (c) at least one compound selected from the group consisting of diglycollic acid and diglycollates.
In still another aspect of the invention, there is provided a method of reducing the kogation of the surface of the heater of the ink-jet recording head of an ink-jet printer, the ink-jet recording head being provided with a heater for applying thermal energy to ink in order to discharge ink from an orifice, the heater having a top surface protecting layer containing a metal and/or a metal oxide, wherein the ink is adapted to ink-jet recording and contains (a) a coloring material, (b) a liquid medium and (c) at least one compound selected from the group consisting of iminodiacetic acid and iminodiacetates.
Thus, according to the invention, it is now possible to effectively reduce the kogation of the top surface protecting layer of the heater. While it is not clear why ink according to the invention provides such an effect, the inventors of the present invention presume that the iminodiacetic acid or iminodiacetates in ink acts on the metal and/or the metal oxide of the top surface protecting layer of the heater and prevents koga from adhering to the surface or promotes decomposition of koga and exfoliation thereof from the surface of the heater.
As a result of an extensive study conducted by the inventors of the present invention, it has been found that the effect of the top surface printing layer is very remarkable when tantalum and tantalum oxide are used respectively for the metal and the metal oxide. If the amount of energy applied to the heater is Eop and the minimal amount of energy that has to be applied to the heater in order to make the recording head discharge ink therefrom is Eth, it has been found that the koga prevention effect is maximized and the ink discharge durability of the recording head is remarkably improved when the amount of energy applied to the heater is so selected as to make the ratio of Eop/Eth satisfies the relationship defined below.
1.10xe2x89xa6Eop/Ethxe2x89xa61.70
In still another aspect of the invention, there is also provided an ink-jet recording apparatus comprising an ink-containing section for containing ink, an ink-jet recording head having a heater for applying thermal energy to the ink led from the ink-containing section and held in the ink path of the head and a means for applying a pulse-shaped electric signal to the heater according to the recording information given to it, the heater having a top surface protecting layer containing a metal and/or a metal oxide, wherein the ink is adapted to ink-jet recording and contains (a) a coloring material, (b) a liquid medium and (c) at least one compound selected from the group consisting of iminodiacetic acid and iminodiacetates.
In still another aspect of the invention, there is also provided a recording unit comprising an ink-containing section for containing ink and an ink-jet recording head adapted to discharge ink from an orifice under the effect of thermal energy, the ink-jet recording head being provided with a heater having a top surface protecting layer containing a metal and/or a metal oxide, wherein the ink is adapted to ink-jet recording and contains (a) a coloring material, (b) a liquid medium and (c) at least one compound selected from the group consisting of iminodiacetic acid and iminodiacetates.
In a further aspect of the invention, there is provided a method of prolonging the service life of a recording head to be used for an ink-jet recording method comprising a step of discharging ink from an orifice by applying thermal energy to ink, the recording head being provided with a heater for applying thermal energy to ink, the heater having a top surface protecting layer containing a metal and/or a metal oxide, wherein the ink is adapted to ink-jet recording and contains (a) a coloring material, (b) a liquid medium and (c) at least one compound selected from the group consisting of iminodiacetic acid and iminodiacetates.